Found a good guide
Turns out the nvidia driver(though it is rumoured to happen on ati cards too) blocks the audio as it tells the tv that audio is coming through the dvi/hdmi port
What you have to do is uninstall drivers if already installed, then spend a minute getting the id code for tv(which is just a small file that tells you id) then add those into a new registry value which you copy and paste from the site at end of this mini guide, then install the driver and reboot pc
Hey presto the audio now works!http://forums.snapstream.com/vb/showthread.php?p=285484
All I would add to the guide is its confusing where to add the registry value, do it near the end of the file.